1. Field of the Invention
The present invention relates to a method and an apparatus for updating software in a radio terminal device. More particularly, the present invention relates to a method and an apparatus in a radio terminal device in a mobile communication system in which a base station and radio terminal devices are connected mutually through radio communication channels.
2. Description of the Related Art
In conventional radio terminal devices, it is already known that updating of software is processed by downloading update-used software (software data which is used for updating software in a device) through a radio communication channel to a programmable ROM, instead of by replacing a memory such as a ROM that contains a control-software or by rewriting contents of the programmable ROM directly with connecting an external device thereto.
FIG. 1A shows the structure of a prior system to modify software of a radiotelephone disclosed in Japanese Laid-Open Patent Application No. 61-220535. In the figure, a ROM 78 stores software necessary to obtain new software data, and a ROM 79 stores software determining whether the software stored in the ROM 78 is correct. Summarizing the software update process in the conventional radiotelephone, under the control of the software in the ROMs 78 and 79, a CPU 76 receives new software transmitted from a software-supply device (not shown), and the software is demodulated by a modem 74. Subsequently, the CPU 76 stores the new software in a main memory 77 and sets the new software as main memory data.
However, the ROM 78 stores comparatively large software that overlaps with the main memory 77, and is related to radio communication controls (for example, a call control and a transmitter-receiver control). In other words, overlapping the software between the ROM 78 and the main memory 77 is not only a waste of memory space in the ROM 78 and in the main memory 77 but also a cause of the increase in the size of the ROM, 78. Consequently, it is difficult to achieve miniaturization and cost reduction of the mobile communication system. Moreover, the ROM 78 must be replaced when software related to control of the radio communication is revised by a revision of communication service.
FIG. 1B shows the structure of a prior radio communication device disclosed in Japanese Laid-Open Patent Application No. 62-38624. Summarizing a case to improve a function of a present operating control-program stored in an EEPROM 88, update-used software is transmitted from a base station and is transferred through a duplexer 83, a receiver 84, and a modem 86. The update-used software is then data-processed through a processor 89 and a RAM 90 to be stored in the EEPROM 88.
The above-described procedure to overwrite the currently operating program with the update-used program has a possibility that the currently operating program might get damaged while the currently operating program downloads the update-used software. Therefore, it is unsafe to update software in such the device.
As described above, the prior method for updating software is nothing but a substitution of downloading the update-used software through the radio line to replacing memory such as a ROM. Furthermore, in the system of Japanese Laid-Open Patent Application No. 61-220535, the large scaled ROMs 78 and 79 are necessary besides the main memory 77, and in the system of Japanese Laid-Open Patent Application No. 62-38624, the method for updating the software is unsafe.